Recently, probing systems utilizing small diameter probes have been used increasingly for subsurface investigations. These probing systems typically utilize a percussion hammer to drive a probe into the ground. The probe is driven to a desired depth by utilizing one or a series of probe rod sections. A first probe rod section is attached to the probe and driven into the ground by applying percussive forces to the upper end of the rod section. After the rod section is driven into the ground, another rod section is connected to the exposed end of the first section and this second section is driven into the ground. Additional rod sections can be utilized in this manner until the probe is driven to a desired depth. The rod sections typically are connected together using a male/female thread arrangement. The upper end of a rod section has a male thread surface which mates with a female thread surface located on the lower end of the rod section above.
In some of the soil probing systems used currently, each rod section has a hollow bore formed along its entire length generally forming an elongated sample tube. The bores of the sample tube sections are in communication with each other when the tube sections are connected together. For example, one such soil probing system is described in U.S. Pat. No. 5,186,263 to Kejr. In that system, a sample tube is utilized with a releasably fixed piston tip which acts as a plug during driving. Rearward movement of the piston tip during driving is blocked with a removable piston stop. In operation, the sample tube is driven into the soil with the piston tip blocking its forward end. Additional sample tube extensions are successively added to the first sample tube to allow driving of the sample tube to the desired depth. At the desired depth, the piston stop is removed to unblock the piston tip. The sample tube with extensions are then driven forward while the piston tip remains at its position with respect to the soil, causing the soil sample to enter the tube. The entire device is then removed from the soil to recover the sample.
In this arrangement, the piston stop includes a piston rod extending rearwardly through the sample tube. The rearward end of the piston rod is received in a through hole in a drive head fixed to the rearward end of the sample tube. In those situations requiring extension tubes to drive the probe further into the ground, the piston stop is preferably a threaded member so that elongated extension rods can be inserted through the hollow probe extension tubes and used to unscrew and withdraw the piston stop at the appropriate time. When necessary, a series of extension rods are inserted through the extension tubes. Each of the extension rods is formed as an elongated cylinder having standard exterior threads at each end thereof. In order to maintain the extension rods in end-to-end relationship, a plurality of extension rod couplers are used. The rod couplers are formed as short hollow cylinders having standard interior threads corresponding to the threads on the extension rods. Thus, the extension rods are connected in series by threadedly engaging associated ends of successive extension rods with a portion of the length of one of the rod couplers.
A significant disadvantage of the above-described arrangement is the time and effort involved in assembling and disconnecting the various probe extension tubes and extension rods, particularly at increased sample depths. As noted above, the sample tubes typically use a male/female thread arrangement so that only one connection is required to couple two sample tubes. However, in order to assemble a pair of extension rods, two separate connections are required to adjoin the rods with the rod couplers. As is apparent, considerable time and effort is consumed by this process, since the extension rods must be threadedly connected to take the soil sample, and then disconnected as the device is removed from the ground. In addition to the time involved, field personnel often experience difficulty in disconnecting the extension rods and must sometimes use wrenches or other tools to complete the disconnection. Thus, a need has arisen to alleviate the foregoing difficulties involved in subsurface investigations.